For many mold operations it is necessary to displace a mold core or stripper transversely to the closing direction of the mold. Thus in a core-type mold the core must be displaced normally in a direction perpendicular to the closing direction from an inner position extending into the mold cavity to an outer position when the mold is opened. Conversely with a stripper-type mold it is necessary to displace the stripper in a direction perpendicular to the opening direction to push the molded workpiece from the mold once it is opened, so that the stripper moves in as the mold opens.
Although it is known to simply provide a separate actuator, such as a separate hydraulic cylinder, to operate these secondary mold parts, the more common system entails providing on the secondary mold part an extension which projects at an angle both to the direction the secondary mold part must move in and to the direction that the primary mold parts move along. This extension is formed with an eye through which passes an inclined rod that is attached to one of the primary mold parts and that itself also extends at an angle to the motion direction of both the primary and secondary parts. When the primary mold parts move apart, therefore, the secondary mold part is displaced appropriately as the inclined rod of the primary part pulls back in the eye of the secondary part.
Such an arrangement does not normally provide for perfectly synchronous displacement of the secondary mold part relative to the primary mold parts unless the various inclined rods and the like are built very robustly. The opening force and, therefore, the force that the inclined closing bolt is loaded with increases with the sine of the angle defined by the inclined bolt. It has been found impracticable to increase this angle beyond 25.degree., to avoid excessive bending of the actuating bolt. This type of actuating system therefore presents several important design problems which mitigate against its use in many systems. Consequently recourse is frequently had to a totally separate actuator for a secondary mold part in order to assure synchronous operation of it.